Low back pain is an Institute of Medicine priority condition for comparative effectiveness research and it remains a particularly important problem for the elderly, an AHRQ priority population. Nearly one-third of the population over age 65 has severe low back pain and it is one of the most common reasons for physician visits. There is a paucity of evidence-based guidelines for the elderly, who have a different distribution of causal conditions than younger populations. Important questions remain unanswered regarding the comparative effectiveness of most commonly used diagnostic tests and treatments. Funded by a $10 million AHRQ/ARRA grant, we have enrolled a large inception cohort of senior patient with low back pain from three geographically and racially diverse HMOs: Kaiser Northern California, Henry Ford Health System and Harvard Vanguard/Harvard Pilgrim. Patients who enroll in the registry complete validated, standardized measures of pain, back-related disability, and health-related quality of life at enrollment and at regular follow-up intervals. The overall gol of our project, the Back pain Outcomes using Longitudinal Data- Extension of Research (BOLDER), is to extend the usefulness and improve the capabilities of the BOLD cohort infrastructure. Using a stakeholder engagement process, we will enhance the current data infrastructure to address stakeholder-relevant questions. Stakeholder engagement will include health system and payer stakeholders at the various sites as well as senior patients with back pain. Specifically, we will extend our existing data infrastructure by collecting longer-term patiet reported outcomes (PRO) and electronic medical record data collected from diverse data systems within and between health systems. We will use stakeholder input to focus our additional data collection on data that will be of greatest value to stakeholders and can address important questions regarding the long-term clinical effectiveness of back pain diagnostic and treatment interventions.